Wednesday, April 22, 2009

Video Display Terminals Ergonomics

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Wright State University

Policy number: 6050

Subject: Video Display Terminals Ergonomics
Date issued: April 1994

Authority: National Institute for Occupational Safety and Health; National Safety Council

Reference: Department of Environmental Health and Safety

6050.1 History

The Ohio Occupational Safety and Health program for public employees has determined that the university is responsible for a workplace that is not harmful to the health and well-being of it's employees.

Extended work at a video display terminal (VDT) may result in an employee experiencing a wide range of conditions including but not limited to headaches, general malaise, and visual and musculoskeletal strain. However, the majority of complaints are eye fatigue, eye irritation, blurred vision, and pain and stiffness in the neck, shoulders, back, arms, wrists, and hands.

6050.2 Purpose

The purpose of this guide is to educate, promote a preventive approach, and attempt to reduce lost time from work.

1. Education. Extended time at a VDT workstation may have a negative effect on the health and productivity of employees who are encouraged to bring to the attention of their supervisors any problems that they may be encountering. The Department of Environmental Health and Safety (EHS) will assist in addressing those concerns and in conducting workstation evaluations. Ergonomically designed furniture is available through the Purchasing department.

2. Prevention. In order to promote a preventive approach, workstation exercises are recommended to provide relief from workplace stress and musculoskeletal strains. EHS will provide brochures and posters. Additionally, to relieve stress and fatigue, the National Institute for Occupational Safety and Health (NIOSH) recommends alternating VDT work with non-VDT work. The National Safety Council and NIOSH recommend the following guidelines for the ratio of VDT work to non-VDT tasks:

Operator VDT Workload Frequency for Non-VDT Tasks Length of Non-VDT Tasks
Moderate (less than 60
percent of operator time looking at screen) Every two hours 15 minutes
Heavy (greater than 60
percent of operator time looking at screen) Every hour 15 minutes


Lost Work Time. Not only does this guide attempt to reduce lost work time due to VDT related problems, it also attempts to reduce workers compensation payments for medical expenses associated with injuries from extended VDT operations.

6050.3 Ergonomics in the Workplace

Workstation design. When designing a workstation, it is possible that more than one individual may use the station; and, therefore, flexibility in the height of the work surface and chair, as well as the reach distance of the operator, should be considered. Upon request, EHS will provide information on general design criteria, arm and wrist supports, as well as ergonomic evaluations.

1. VDT height. The optimum height of a VDT for operator comfort is approximately 28 inches from the floor to the normal rest position of the operator's fingers. This height permits the operator to sit with arms nearly horizontal, shoulders comfortably relaxed, and wrists at the proper angle.

2. Keyboard. The keyboard should be located so that the upper arms hang straight down from the shoulders and the forearms are horizontal or lower.

3. Screen. The screen should be placed in order that glare is kept to a minimum, the operator's line of sight is horizontal to 20 degrees down and falls comfortably in the upper half of the screen, and a distance of 15 to 20 inches from the operator's eyes is maintained.

4. Chair. The chair should be in a position so that the thighs are permitted to rest approximately horizontal without being pinched by the front edge of the chair, the calves hang vertically, and the feet rest squarely on the floor or on a footrest.

5. Illumination. A general room lighting level of 500-700 lux (50-70 foot candles) is normally recommended in the vicinity of VDT workstations, but may need to be higher depending upon the visual demands of other tasks performed in the same work area. Glare is a common problem at VDT workstations and can be very discomforting to the operator, as well as have a negative effect on productivity. To reduce glare, drapes, shades, and/or blinds over windows should be closed, especially during direct sunlight. The terminals should be positioned so that glare from windows and overhead lighting are not reflected on the VDT screen. Screen hoods may be installed to shield completely or partially the screen from reflection. Anti-glare filters may be installed on the VDT screen. Direct lighting fixtures may need to be recessed and baffles may be used to cover light fixtures to prevent the luminaries from acting as a glare source, or special covers on light fixtures may be used to direct the light downward rather than allowing the light to diffuse.

6. The following figure illustrates an ideal workstation design.


6050.4 Eye Examination

1. Employees who meet the following criteria should have an eye examination before beginning VDT work and be tested annually thereafter.

1. An employee's job description must list VDT operations as a requirement of the position. VDT operations must be continuous for four or more hours per day and be a single detailed task. Exception: An employee who wears tri-focal lenses and is required, as part of his/her job description, to operate a VDT should be encouraged to have an eye examination regardless of the number of hours spent per day at a VDT station. Employees who wear tri-focal lenses normally experience visual fatigue and musculoskeletal stress after relatively short operating times at a VDT. An eye examination for those individuals will determine if mono- or bi-focal lenses can be prescribed and worn by those employees for VDT operations. Additionally, an employee must have completed his/her probationary period.

2. When an employee believes that he/she meets the above criteria and is eligible for an eye examination, the employee should bring that fact to the attention of his/her supervisor.

3. The immediate supervisor shall review the job description and daily work activities of an employee to determine if the criteria for an eye examination has been met. If the immediate supervisor cannot reach a decision, the Department of Human Resources shall make the final decision.

4. An eye examination shall meet the recommendations of the latest guidelines published by the American Optometric Association. The Department of Environmental Health and Safety will, upon request from an employee's supervisor, provide a list of the recommended tests.

5. An examination may be given at any qualified location, provided the American Optometric Association recommended tests can be conducted.

2. Payment for an eye examination

1. An employee and his/her hiring department will each pay 50 percent of the cost of an eye examination.

2. An employee shall pay the full cost of new eye wear including lens and frames.

3. The university is not obligated to pay any portion of an eye examination that does not include all of the American Optometric Association recommended tests [refer to paragraph 6050.4 a) 4)].

6050.5 Additional Information

Additional information and an ergonomic evaluation may be obtained from the Department of Environmental Health and Safety, 104 Health Sciences Building (775-2215).